My model has flickering weird shadows?
Looks like you have view clipping issues. In your properties panel on the right-hand side of the viewport (N) you should see a 'View' section. I suspect you have set the 'Clip Start' and/or 'Clip End' to an extreme value. Try adjusting those to something realistic to your scene (eg, 0.001m Start, 1000m End).
Blender uses the Clip Start and Clip End in calculating distances but only has a limited precision for holding and calculating values. If you use extreme ranges Blender is unable to calculate intersections and edges accurately and you see artifacts such as what you are seeing. By choosing a more reasonable range Blender can apply suitable precision and the artifacts are no longer visible.